Hong Kong -LRB- CNN -RRB- -- Signs of oil and gas have been found by a Chinese rig that was drilling off a disputed island chain in the South China Seas , according to Chinese state media .

The drilling area does have the basic conditions and potential for oil exploration , Wang Zhen , deputy director of CNPC Policy Research Office , told Xinhua .

The drilling operation , known as the Zhongjiannan Project , was completed on July 15 , according to the China National Petroleum Corporation -LRB- CNPC -RRB- . The state-owned energy company will further analyze the collected geological data before announcing their next steps .

When China dispatched the oil rig on May 2 to begin drilling near the Paracel Islands in the South China Seas , the move kicked off a series of confrontations between Chinese and Vietnamese vessels in the area . Both nations claim ownership over the chain China refers to as the Xisha islands .

Rioting

Clashes at sea sparked violent anti-Chinese riots on land . Thousands of Chinese nationals had to be evacuated from Vietnam in mid-May as the demonstrations turned deadly .

In the face of Vietnam 's ferocious protests , Beijing has stood its ground on its claim over the Paracels .

China 's Ministry of Foreign Affairs spokesperson Hong Lei emphasized this on Wednesday .

`` The Xisha Islands are integral parts of China . The operation by the Chinese company is located in indisputable coastal waters of the Xisha -LRB- Paracel -RRB- Islands , which falls well within China 's sovereignty , '' said Hong .

Xinhua also reported that 13 Vietnamese fishermen previously arrested by the Chinese coastguard were deported on Tuesday . The fishermen were accused of operating illegally in Chinese waters off the coast of Hainan Province .

Vietnam continues to reject China 's claims to the Paracels , calling recent drilling activities `` illegal '' and in violation of international law .

According to CNOOC , a third of China 's oil and gas resources are under the South China Sea , most of which it claims as its own , refuting rival claims from Vietnam , the Philippines , Taiwan , Malaysia , and Brunei .

@highlight

China completed a drilling operation near the Paracel Islands between May 2 and July 15

@highlight

The area has potential for oil exploration and is contested by China and Vietnam

@highlight

China recently deported 13 Vietnamese who were arrested for fishing in Chinese waters